Megafauna Extinctions.

Megafauna Extinctions .
Andre Willers
18 Dec 2010

Synopsis :
Mainly America , Australia .
Humans did not cause the extinctions , but exploited the ecological gaps opened by the extinctions . Hence the temporal uncertainty . Extinction first , then quick human exploitation , stabilizing the ecosystem . Human guilt is over-driven .

Discussion :
1.Human conceit .
Humans think they can just walk into an existing ecosystem in it's full maturity and upset the applecart with a few puny tools .

Marketing analogue :
A new organism entering an established ecosystem face the same problems as a new product being foisted upon an existing economy .

Ask any foreign marketing executive how difficult it is to break into a fully developed local economy . Deep pockets and sustained effort is needed . The mathematics and economics have been exhaustively studied . I see no reason to re-invent the wheel . Look it up .

(Look at how tenuous the hold of the early settlers in North America circa 1600 AD really was .)

The human family-groups trickling into North-America or Australia over long periods went extinct or hung on by their fingernails .

2.The Extinctions :
Something drastically altered the ecosystems . Suddenly , humans could survive in more numbers . They enthusiastically exploited the gaps . This might have caused some extinctions , but the initial impetus was external .

2.1 North America
Humans trickle in via Bering strait , but hang on by their fingernails .
Extinction event : Comet fragments impact circa 13 000 ya .
Evidence of impact craters and impact sphericules have been found .
Ecosystem drastically affected .
Human numbers explode as competition for niches decline .
Surviving megafauna hunted to extinction .

Note that diseases would not have played a major role , as the Bering-landbridge allowed contact .

2.2 Australia
Humans trickle in via North Australia , mainly hunting parties .
With them comes rats , birds and marsupials from the Asiatic mainland . As Jared Diamond would say , they had no guns or steel , but germs they had . The Australian continent had been isolated from the pestilential breeding-grounds of Asia . Now these diseases sweep through the Australian continent over a period of thousands of years , severely impoverishing the local ecosystems . (Circa 70 000 – 45 000 ya)
Humans then move in and hunt the few survivors to extinction .
But the local ecosystems remain impoverished till today .

2.3 Africa
It is usually pointed out that it did not happen in Africa because of some mutual adaptation between humans and animals . (Diamond)

Rinderpest .
Unfortunately , it did . Called Rinderpest . (Circa 1890 AD)
A bovine disease that followed an Asia->Europe->Africa route that killed more than 90% of African bovines . This was an event whose ramifications are still working its way through the African ecosystem.
The human effect was of genocidal proportions .
Easily on par with the Australian extinction event .
See en.wikipedia.org/wiki/Rinderpest

Notice the speed , ferocity and effectiveness of the reaction . Rinderpest has been eradicated . Killing cattle activates some very old memes (Celtic , Bantu , etc)
Humans can do something right if they really , really try .

2.4 Euro-Asia
The same thing happened on an accelerated timescale . Every time a Virtual Continent was created and isolated (ie an Empire) , a Plague of some sort comes along , breaking the borders .

3.Summary :

3.1 As a Strategy , better communications with localized quarantine seems superior to prevent a large scale Extinction-level events . Chop it up into little Events . The present strategy .

3.2 Human guilt :
Overdone , to put it mildly .
A good argument can made that humans actually prevented a deeper collapse of the eco-systems by aggressively moving into and managing the vacated niches .

Nothing could have saved the megafauna of North-America or Australia once their ecosystem had fallen below a certain level . This was not caused by humans .

A quick eradication of top-level herbivores and predators enables a fast recovery to a less complex ecosystem . At least there is something , not just a desert , as could easily happen as top-level organisms battle for sustenance in an already impoverished ecology .

As for the bacteria and viruses , might as well blame Life or Gaia . Things change .
Humans are just better at exploiting and managing change .

Intriguing speculation :
The mass-shooting of game in Southern Africa circa 1900 AD might have been necessary to stave off a collapse of the grass-lands . These grasslands depend on herbivore dung to fertilize them . Needless to say , large numbers of herbivores are needed . But there is a theoretical maximum of herbivores , derived as follows on a first iteration :
Dung ~ nHerbivores
But also Dung ~ (nCarryingCapacity – nHerbivores)
Thus , Dung ~ nHerbivores *(nCarryingCapacity – nHerbivores)
This gives a quadratic equation on nHerbivores , with a maximum .
This means that you can always find an optimal number of herbivores for any given grass feeding ground .
Herbivores = game + cattle .
Rinderpest hit cattle far harder than game . In the short term it meant less dung from cattle , hence smaller carrying capacity of the land . In the long-term this would have been compensated by increased births of game . But these were managed farms . The niche for future births had to be left open to cattle . Thus game numbers had to be reduced .

In other words , if it had not been done , large parts of south Africa would now be desert .
The real argument is much more complex , but this is the gist of it .

Did collapse of the grasslands happen in other parts of Africa ?
I do not know , but suspect that many aspects of desertification can be traced to this cause . The effects are still working through .
Just another result of Rinderpest and human attempts to manage the effects .


4. Surprising Verdict :

Not Guilty !

Amerindians and Australian Aborigines were Not Guilty of killing off their Megafauna .

Instead , for sheer survival , they had to run around and cobble up a workable eco-system out of the ruins , with very few tools and little understanding . They did a fair job .

This resolves quite a number of niggling inconsistencies between the way the Amerindians and Aborigenes saw themselves (as custodians and sharers ) , contrasted to some other interpretations .

Fiat iustitia coelum ruat .

Andre